This invention relates to improved tamper resistant push on assemblies for containers. It is particularly useful in connection with re-usable glass bottles such as milk bottles, but not necessarily limited to such use.
Bottles in the nature of milk bottles were conventionally closed by means of friction fitted cardboard disks, crimped on aluminum foil caps and crimped on paper caps, none of which are tamper resistant.
Although there had been described a number of tamper resistant closures for screw bottles, as for example shown in U.S. Pat. No. 4,394,918, we did not regard it as practical to convert re-usable glass bottles such as milk bottles to screw type bottles simply to allow existing tamper resistant closures to be used, given the major capital cost involved in such conversion. Moreover, as a result of the relatively large diameter of the necks of bottles of this type and the relatively wide tolerances to which such bottles are manufactured, it was also viewed as impractical to construct tamper resistant closures on the basis of expedience such as ratcheting teeth.
With a view to providing a one piece molded tamper resistant push-on closure particularly suited for closing glass bottles which would be readily adaptable for use with existing closure machinery, we earlier devised the closure described and claimed in our U.S. Pat. No. 5,875,908. That one piece molded tamper resistant push-on closure comprises a latch ring portion and a cap portion, the latch portion including a plurality of integral, upwardly inwardly angled teeth for snap retaining the latch ring portion beneath a shoulder associated with the bottle when the closure in pushed onto the bottle, while restricting detachment of the closure therefrom. The latch ring portion and the cap portion of the closure are connected by a plurality of frangible tabs, some of which serve to retain the latch ring portion in the form of a closed annulus. The cap portion includes a pull tab disposed on a peripheral portion thereof. By exerting a moderate force on the pull tab the aforementioned frangible tabs are ruptured, opening the annulus to permit the latch ring portion to be moved transversely from engagement above the neck of the bottle.
We have since discovered that, with certain types of bottles having particular contours and dimensions of the upper rim of the bottle and the shoulder below the upper rim it is occasionally possible, with some effort, to prise a closure according to the ""908 patent from the bottle, without rupturing the frangible tabs so as to provide clear visual evidence of tampering.
In order to provide a one piece molded tamper resistant push-on closure that is suited for closing glass bottles such as milk bottles, even where the rim and shoulder shape associated with the bottle opening are unusual or irregular, we found it advantageous to design more aggressive means for locking the closure in place, but without diminishing the ease of legitimate removal of the closure by tearing away the latch ring.
It is an object of the present invention to provide such an improved one piece molded tamper resistant push-on closure for glass bottles which need not be assembled on the neck of the bottle and which is readily adapted for use with existing closure machinery.
It is another object of this invention to provide such closures with frangible members that can be ruptured without the necessity of using excessive force.
It is still a further object of this invention to provide such closures that are easily removable to permit the re-use of the bottle.
In accordance with a broad aspect of the invention, a one piece molded tamper resistant push-on closure suitable for closing glass bottles comprises a latch ring portion having an upper and lower peripheral margin, an inwardly directed surface extending therebetween, and a plurality of circumferentially spaced slots therethrough. A plurality of resiliently deformable teeth depends from the latch ring in an upwardly inwardly direction relative to the interior surface thereof, each said tooth presenting on its surface an integral bead of a shape and disposition adapted to project through a corresponding one of said slots through the latch ring portion as the latch ring is engaged onto the neck of a bottle.
The closure of the invention further comprises a cap portion having a lower peripheral margin and an inwardly directed surface extending upwardly from the lower peripheral margin thereof. A plurality of frangible tabs connect between the latch ring portion and the cap portion. A manually engagable tab integral with the latch ring portion projects outwardly from the latch ring portion. Application of a suitable manual force to the tab with progressively rupture the frangible tabs and permit the cap to be removed from the bottle to which the closure has been applied.
In this arrangement, force exerted on the projecting tab is applied at one radial point rather than about the whole of the periphery of the cap and results in the more or less serial rupture of the frangible tabs, rather than their being ruptured simultaneously. Accordingly, it is found that the force necessary to disengage the cap from the latch ring using the manually engagable tab is well within the capability of the average person, while the cumulative force is sufficiently high as to reduce the likelihood of an inadvertent detachment.
In a preferred embodiment, the manually engagable tab is in the form of a part-parabolic convex projection having a rearward truncated wall surface acutely angled to a diameter of the closure therethrough for comfortable accommodation of the tip a user""s thumb or finger, affording the grip and leverage needed to break the first frangible tabs and so permit tearing away of the latch ring portion.
Generally speaking, the upper end of the cap portion will be in the form of a flat dome, and suitably a stopper will depend downwardly from the dome to provide a liquid tight seal with the interior surface of the bottle. Desirably, the stopper will have a tubular cross-section so as to be resiliently deformable and accommodate normal variations found in glass milk bottles, for example. Also preferably, the stopper will have a maximum external diameter intermediate the axial ends thereof so as to facilitate the initial engagement of the stopper in the neck of the bottle and to localize sealing forces.
Also preferably, the latch ring is in the form of an open annulus which permits is ready removal from the neck of a bottle once the frangible tabs have been ruptured.
The foregoing objects and aspects of the invention, together with other objects, aspects and advantages thereof will be more apparent from a consideration of the following description of the preferred embodiment thereof taken in conjunction with the drawings annexed hereto.